I believe this can be used to revise prepositions and/or Present Continuous at elementary/pre-intermediate levels. I ask the students to work in a few mini-groups and invent a funny picture of a 'mess'in the classroom. They may focus on the fact that everything is in the wrong places. To revise or practise the Present Continuous, I ask them to imagine the other members of the group doing something wrong and to give a detailed description. The secertaries note down the descriptions, and then the students present them. The group whose mess is the messiest wins!